Author: Robert Hyatt
Date: 08:28:14 05/18/98
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On May 18, 1998 at 09:49:40, Peter Fendrich wrote: >Has anyone tried this? > >I found the following description at: >http://www.xs4all.nl/~verhelst/chess/search.html#enhanced-transposition >---------------------------------------------------------------- >There may be several successors causing a cutoff and we want to use the >one with the smalles search tree. One idea that has been tried is to >look at all successor positions and see if they are in the transposition >table and cause a cutoff. If one such position is found, no further >serach has to be done. >This can save about 20-25% in total tree size. >---------------------------------------------------------------- > > >//Peter I tried it about 2 years ago... It does two things: (1) it will reduce the size of the tree searched by about 10% according to the tests I ran way back then. (2) it breaks programs that generate moves in batches, because you can't... you have to generate *all* the moves, and use each move to produce a new hash signature that you use to probe the hash table to decide which move to try. In Crafty, this cost me more than that 10% saving in nodes searched. If you always generate all the moves (Cray Blitz did because the moves were vectorized) then this works, and we used it there with success. But if you defer move generation as I do in crafty, by generating only captures, and then trying killers before generating non-captures, you lose the benefits of that. A program like dark thought that "generates as needed" would probably slow down even more, assuming it still generates moves a few at a time.
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